Hot-swapping pluggins

[olanod]

When running Valor in the web specially, it will be very useful to swap one plugin with another that has the same API but changes its implementation in some way, for example one could quickly load the runtime and create an instance of the Sube plugin that uses the lightweight HTTP backend to connect to a remote node and in parallel download the heavier version of the plugin that uses a light node as a backend and once it's downloaded and ready one can swap the HTTP version for the lightnode without the client application realizing there was a change, if the application wants to be more transparent with the user it could install the heavier version only after prompting the user to install the application.